PSTricks: Newly introduced error in package

Update

This fix is no longer needed in current tex systems. MikTeX users should keep in mind that they may have to run the updater in admin and user mode in case the involved packages reside in different trees of a multi-user installation.

Old Answer

Until pstricks has been adapted to the new pgf version you could try to replace in a local copy of pstricks.tex (you find it in tex/generic)

\def\ProvidesPackageRCS{\@ifnextchar[\ProvidesPackageRCS@i{\ProvidesPackageRCS@i[] }}%$ 

by

\def\ProvidesPackageRCS#1{}

use pstricks.tex from http://archiv.dante.de/~herbert/texnik/tex/generic/pstricks/ or wait one or two days for the update. It has a slightly other solution.

For texlive-pstricks in MacPorts, it worked to uninstall and deactivate pgf and then install pgf-devel (on 2019-03-15).